Automated External Defibrillators (AEDs) have been available for public use for several years, and have proven effective at treating Sudden Cardiac Arrest (SCA). SCA kills about 250,000 Americans a year and is the leading cause of death in the U.S. Untreated SCA usually results in death in a very short time, and survival rates for SCA decline by about 10% for every minute defibrillation treatment is delayed. Because most EMS or other medical response cannot reach the scene of SCA within a very few minutes, it is important for witnesses or bystanders to be able to apply defibrillation treatment as quickly as possible, whenever a defibrillator is available.
Cardiopulmonary resuscitation (CPR) is often performed concurrent with AED use. CPR is a combination of artificial respiration and artificial circulation that keeps oxygenated blood flowing to the brain during cardiac arrest. The effectiveness of CPR is highly dependent on the proficiency of the rescuer's application, and as such, the AHA and American Red Cross have established detailed step-by-step CPR procedures. Many people receive CPR training each year, but most, even emergency responders, have not maintained their proficiency. Rescuers may find it difficult to recall these procedures, especially during high stress rescue situations and as standards evolve.
Similarly, successful defibrillation requires the rescuer to perform a specific sequence of steps in order for the AED to function properly. The rescuer must activate the AED, remove interfering clothing from the victim's torso, successfully apply the defibrillation electrode pads in their proper locations on the torso, and cause the defibrillation shock to be delivered in order to defibrillate the heart. The victim's chance of survival improves greatly the faster these steps are completed.
AEDs are increasingly being deployed into environments where a minimally-trained or untrained user is likely to be the first responder. AEDs now appear in businesses, schools, public venues and homes in addition to the more traditional emergency responder, ambulance and rescue squad environments.
The problems of minimal training, high levels of stress accompanied by noise and confusion, and a very limited time in which to effect a rescue negatively affects the chances of a successful rescue. The rescue of an SCA victim is a high stress event. In order to keep the rescuer on track during the stress of a rescue, many AEDs guide the user through the defibrillation process with audible or visual prompts. These prompting features are very useful to a user who is unfamiliar with the defibrillation procedure or with CPR protocol. An example of a defibrillator with automatic CPR prompting features is described in U.S. Pat. No. 6,356,785 by Snyder et al., titled “External Defibrillator with CPR Prompts and ACLS Prompts and Methods of Use”, which is incorporated herein.
On the other hand, the same prompting features can delay a proficient rescuer who is able to work faster than the prompts, or can complicate the already chaotic rescue situation with extraneous and distracting information. In some cases, the continuing prompting noise may tempt a rescuer to turn the AED off when a perceived “safe” time in the rescue is reached. If the SCA recurs, the AED then would not have the ability to sense or respond to the recurring emergency.
Thus, there is a need for an AED which provides appropriate information only when it is needed, with minimal action by the user. Specifically, what is needed is an improved AED which selectively provides rescue information to the user in order to reduce confusion and improve the guidance for successful cardiac rescue. Further, an improved AED which can dynamically alter the guidance provided to the rescuer based on both the state of the rescue and on whether or not the rescuer has requested guidance during that rescue state could improve the chances of a successful SCA treatment.